This afternoon, an international task force will invade Jersey. A party of activists from Britain, Italy, France and Ireland will land on the island and take control of St Paul's centre in the capital St Helier, holding a public meeting with local protest groups from 6.45pm. The following morning, there will be a brief tour of a number of offshore bank subsidiaries before the task force hands the island back to its inhabitants.

The invasion plan is part of the ongoing campaign to highlight the damage done by tax havens to national economies. In the latest figures published by the TUC, Jersey was identified as the number one centre for tax dodging by individuals seeking to avoid payment of their UK dues. It is also an important centre for corporate tax dodging. The big four high street banks (RBS, Lloyds TSB, Barclays and HSBC) have 170 subsidiaries based in Jersey, making it the second most popular tax haven for banks behind the Cayman Islands.

It is important to be aware of the full extent of the challenge posed by tax dodging, as much of the recent reporting in the Guardian has focused on isolated aspects of the problem. When tax avoidance, tax evasion and non-payment of declared taxes are added together, the loss to the UK exchequer is estimated at a staggering £100bn each year. Yet rather than boosting capacity to pursue this lost revenue, the Labour government intends to close over 200 tax offices across the UK, with the loss of 25,000 jobs.

With pressure mounting, Jersey has now rushed to sign a tax information sharing agreement with the UK, in the hope that it can escape being on the blacklist of tax havens being drawn up in advance of next month's G20 summit. Gordon Brown, who has found himself increasingly out of step with world opinion on tax, has also been forced into a U-turn to avoid being isolated at the London summit. Despite his previous attempts to deflect attention onto Switzerland and other secretive jurisdictions, the prime minister has now been made to accept that the clean-up must start at home.

Brown is clearly vulnerable because of the central role that Britain plays in facilitating corporate tax dodging. While the IMF has already named London as an onshore tax haven, crown dependencies such as Jersey, Guernsey, the Isle of Man and overseas British territories such as the Cayman Islands, Bermuda and British Virgin Islands are all listed as "offshore secrecy jurisdictions" in the new US legislation against tax havens which is soon to be put before Congress. The draft law, which is backed by President Obama, identifies these jurisdictions from previous court cases as "probable locations for US tax evasion".

The impact of tax dodging on the economies of the rich world is bad enough. For poorer countries, the consequences of corporations failing to pay their dues is catastrophic. Estimates suggest that developing countries lose up to £250bn each year as a result of corporate tax dodging. This includes not just the amounts tucked away into tax havens but also the sums lost to scams such as transfer pricing, where multinational corporations shift goods and services between subsidiaries in various jurisdictions and fabricate charges in order to avoid paying the tax due.

The invasion of Jersey is the first of a number of actions planned in the run-up to the G20 summit, including the major national demonstration on Saturday 28 March and the activities in the City of London on Financial Fools' Day. As G20 finance ministers meet in London this coming weekend, they must realise that fine words and emergency stimulus packages are not enough to satisfy the call for global justice. Decisive action to end the scandal of tax havens would be a good place to start.